Microscopia de Iones y Nano-Tecnología

Eduardo H. Montoya Rossi

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• The Focused Ion Beam (FIB) Instrument.

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• The FIB column.

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• How the FIB works.

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• How the FIB works.

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• What is it possible with FIB?

• Micromachining.

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• What is it possible with FIB?

• FIB tomography.

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• What is it possible with FIB?

• Material deposition.

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• What is it possible with FIB?

• TEM sample preparation.

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• Sample preparation is a critical step in Transmission Electron Microscopy (TEM) studies.

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• Conventional techniques have been used for long time.

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• New, state of the art, transmission electron microscopes require ultra high quality samples, “free from any surface damage and with negligible surface roughness” (Genç et al. Microscopy & Microanalysis, 13:1520-1521, 2007).

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• Constant thickness is required for quantitative transmission electron microscopy (TEM) methods.

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FIB preparation of a TEM specimen:

• A thick lamella is machined by focused ion beam milling.

• Then extracted (lift out) by a needle.

Bulk sample surface

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FIB preparation of a TEM specimen:

• The specimen is welded to a TEM grid and released from the needle.

• Then thinned by low current and low energy FIB milling.

• The result is a (high quality?) TEM lamella.

BF - TEM

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FIB – TEM on mono-crystalline Ge

• Difficult case• Top: S. Rubanov & P.R.

Munroe. Micron, 35:549 – 556 (2004)

• Bottom: present work.

HRTEM

HRTEM

HAADF-STEM Finished at 5 keV

Finished at 5 keV

Finished at 10 keV

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•S.

Bals

, u

npublis

hed

Ion milling – HRTEM on LAO / STO multilayer

LA

OST

O

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LAO / STO multilayer: HRTEM

• FIB

LAOSTO

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Double cross sectional study: Examining the cross section of the cross section.

• Provides direct measurement of the thickness of a FIB prepared TEM specimen.

• Provides information about the thickness, origin, structure and composition of the damaged / amorphous layers induced by the FIB preparation process.

Why is it important?

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Double cross section technique

1. Cover both sides of the specimen with sputtered Au.

2. Embed the Au-covered specimen in a Pt brick.

3. Cut slices from the Pt brick.

Grid horizontally

mounted

1

2

2

1

1,2: observation directions

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Proposed procedure is clean, easy, fast and reliable

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Double cross sectional study: LAO / STO

HAADF-STEM

• Specimen thickness is fairly constant inside the Region of Interest (ROI).

• Bottle like shape of the cross section.

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• ROI: HAADF-STEM image (A) and EFTEM maps of Ti, La and Ga (B, C).

• Spreading of La (B) and enrichment of Ga (C) in amorphous layers.

• Boxes indicate regions selected for intensity scan plots (next slide).

Double cross sectional study: LAO / STO

FIB Au

Au

HAADF-STEM EFTEM EFTEM

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• Question marks (A): La and Ti signals not detected by HAADF-STEM.

• These signals correspond to redeposited amorphous material.

• Peaks of La at borders of original specimen cross-section (B).

Intensity scan plots across (A) and along the multilayer (B).

Double cross sectional study: LAO / STO